The present invention relates to a fuel injector.
German Published Patent Application No. 196 25 059 describes a fuel injector having multiple fuel channels in a flow path of the fuel from a fuel inlet to an injection orifice, the cross section of the channels determining the amount of fuel injected per unit of time at a given fuel pressure. To influence the fuel distribution in a fuel cloud injected, at least some of the fuel channels are oriented so that the streams of fuel coming out of them are injected directly through the injection orifice.
One disadvantage of the fuel injector known from the publication cited above is in particular the fact that the fuel channels are situated in a plane perpendicular to the direction of flow of the fuel, i.e., the orifices are situated on a circle around a valve needle guide connected to the valve-seat member. In this way, the quantity of fuel flowing through the fuel injector is not metered accurately enough when the valve-closure member is lifted up from the sealing seat.
Furthermore, the number of bores is not sufficient to produce a sufficiently homogenous fuel cloud which meets stoichiometric requirements for complete combustion. This is further reinforced by the large diameter of the fuel channels.
The fuel injector according to the present invention has the advantage over the related art that a turbulent flow created by the fuel flowing through the fuel channels into the swirl chamber remains homogenous in the circumferential direction without any compensatory measures, the volume of the swirl chamber being so small that it is possible to maintain the turbulent flow even during the dead time of the fuel injector.
It is advantageous in particular that the large number of fuel channels ensures a very homogeneous cloud of mixture.
The fuel channels are advantageously formed in a hollow cylindrical valve needle guide which is either designed in one piece with the valve-seat member or is connected to it so that eccentricity and tilting of the valve needle are prevented.
The design of the fuel channels in an annular insert which is insertable into the valve-seat member is especially simple to manufacture and may be used for any desired designs of fuel injectors, because the valve-seat member need only have a cylindrical recess to accommodate the insert.
The shape of the swirl chamber, which is designed as a recess on the injection side of the insert, is also advantageous. Any desired volume may be obtained by appropriate lathing or similar machining and adapted to requirements.